Radio receiving system



J1me 9 A. N. GOLDSMITH RADIO RECEIVING SYSTEM Original Filed June 15. 1918 z; 2: Fig.6.

T m a/ a m mm W Z W His Attohneyv Patented June 11,1929.

UNITED STATES PATENT OFFICE.

ALFRED N. GOLDSMITH, OF NEW YORK, N. Y., ASSIGNOR '10 GENERAL ELECTRIC COMPANY, .A CORPORATION OF NEW YORK.

aamo RECEIVING SYSTEM.

Original application filed June 15 1918, Serial No. 240,199. Divided and this application filed November My presentinvention relates to radio signaling systems and particularly to apparatus for receiving and amplifying radio signals. The object of my invention is to provide a convenient, efficient and simple apparatus for receiving radio signals which will avoid the necessity of using thecustomary large and elaborate elevated antenna system which is ordinarily employed. A further object of my invention is to provide an apparatus which may ea ily be adjusted or tuned to the frequency of the signal which it is deslred to receive.

In carrying my invention into effect I employ a receiving coil havin such values of, distributed capacity and in uctance that the coil as a whole'is resonantto the frequency 'of the waves which itis desired to receive. I also provide means for adjusting the values of the capacity and inductance of the coil in such a way that the same apparatus may be used for receiving signals of different wave lengths without any necessity for the use of a separate condenser such as is ordinarily employed for tuning the receiving system.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, to-

gether with further objects and advantages thereof will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figs. 1, 2 and 3 illustrate the current.

and voltage relations in receiving coils under different conditions of operation; Figs. 4, 5 and 6 illustrate diagrammatically different methods of adjusting or tuning the receiving coil to the desired frequency; Fig. 7 illustrates the use of one of my receiving coils as the secondary of a transformer for obtaining high voltages with small energy input, and Fig. 8 shows diagrammatically a receiving system in which my receiving coils are employed in combination with a plurality of amplifiers and a detector for receiving radio signals.'

It is well known that if a stationary wave is produced on theus al vertical antenna Serial No. 675,000.

systemthe voltage at the extreme end of the antenna is a maximum and at the ground end is zero while the current at the extreme end is zero and at the ground is a maximum. It is also known that the behavior of a coil such as the coil 1 of Fig. 1 having large distributed inductance, large distributed capacity, small resistance and small dielectric conductance between turns is very similar to that of a vertical antenna except in one\important particular. For a given length of wire the natural wave length of the coil will be considerably greater. The reason for this is that theory and experiment agree. in giving the velocity of propagation of electromagnetic disturbance in a conducting system as inversely proportional to the square root of the product of inductance per unit length by capacity per unit length. Since this product is much greater for the coil the velocity of propagation of such a disturbance along the coil is much less than for the antenna. As a result, since the wave length of the antenna or the coil is dependent on both the frequency and the. velocity of propagation, it will be possible to build in very moderate dimensions a. coil which will have the same type of non-uniform current and voltage distribution along its length as does the antenna. that the voltage at the top 2 of the coil 1, which has large distributed capacity and inductance, is, for a. given current at the foot It is known in addition 3 of the coil greater, the greater the inducit will be an antenna system in that, whentraveling electromagnetic waves strike it, if

their frequency and its own natural frequency are identical, a stationary wave will be set up in the coil with. the current and voltage distribution indicated by the lines fraud 6 respectively. Furthermore the .coil willact as the tuned secondary which is usually provided in receiving systems by placing a condenser across theterminals of the coil which s ordinarily coupled to a coil,

in the antenna. In other words, the system shown in Fig. 1 consisting of a single compact coil replaces the usual antenna system with primary and secondary coils and secondary tuning condenser. I have shown the end 3 of the coil grounded but the potential of this end may be fixed sufliciently for practical purposes by merely attaching it to a conductor having large capacity without any actual ground connection.

It will be apparent from the above description that a coil of the nature described will operate in a manner strictly analogous to the manner of operation of the usual tuned much greater than the voltage available in previously used systems.

' A further modification of my invention whereby the same coil may be used for several frequencies or wave lengths is indicated in Figs. 2 and 3. Fig. 2 indicates the-manner in which a wave of half the original wave length may be received by grounding the middle point of the coil 1 at 7, or connecting to the middle point 0f the coil 1 at 7 or connecting to the middle point a conductor of large capacity. The current and voltage distribution on the coil in this case are indicated by the lines 8 and 9 respectively. Points 7 and 10, 7 and 11, or 10 and 11 would be connected" in this case to the input circuit of a potential operated detector or amplifier. In Fig. 3 the current and voltage distribution curves for a wave of quadruple frequency or one-fourth the original wave length are indicated by the lines 12 and 13 respectively. Points 14 and 15, for example, may be connected to the input circuit of the detector or amplifier.

In Fig. 4 I have indicated a simple manner for constructing the coil so that the natural wave length may readily be varied. In this case the coil is made up of three portions 16, 17 and 18 connected together and mounted upon an axis 19. 20 and 21 are the terminals of the complete coil. The separation between the portions 16, 17 and 18 may be made continuously variable in any suitable way as by moving the coils longitudinally along the axis 19 to vary the distributed capacity and inductance of the entire coil. That is, the greater the' distances between the separate portions of the coil the less the inductance and the capacity and the-shorter the natural wave length. The arrangement shown in are mounted on a curved axis so as to be capable of rotation with respect to one another as well as separation. Still another arrangement is shown in Fig. 6 in which two movable portions 22 and 23 of the coil are adapted to be moved laterally with respect to the fixed portions 24 and 25. While I have illustrated three different ways of adjusting the coil to accomplish the desired result I do not wish to be limited to the particular methods shown as it will be apparent that the necessary adjustment may be brought about in many other ways.

I have illustrated diagrammatically in 7 the use of one of my coils as the secondary of a transformer for obtaining high voltages when only small outputs are available. In this case 26 and 27 are the input terminals and 28 the primary of the transformer of which the coil 29 forms-the secondary. The coil 29 has such distributed constants that it is resonant to the frequency impressed upon the primary 28. Then a relatively high voltage will appear at the,

terminals 30 and 31 the potential distribution I being indicated by the line 32.

In Fig. 8 I have illustrated acomplete receiving station. Coil 33 is a coil of the type described and illustrated in Fig. 1, and is connected to the input circuit of the electron discharge amplifier 34. This amplifier amplifies the energy received by the coil 33 and a transformer primary 35 in its output circuit supplies the amplified energy to the coil 36 which is included in the input circuit of a second electron discharge amplifier 37. The transformer which is made up of the coils 35 and 36 corresponds to the one illustrated in Fig. 7, and serves to transform the voltage variations in the output circuit 3f amplifier 34 to much higher voltage variations. The amplified energy variations in the output circuit of amplifier 37 are supplied by means of the transformer 38 to a detector circuit comprising a detector 39 of any desired form, and

the usual'telephone receiver 40. The con nection of the grid and filament of the amplifiers to the terminals of coils 33 and 36 will affect slightly the natural. frequency of the coil but this may easily be compensated for by slight readjustment. It will, however, be desirable to keep the-added capacity of the detector or amplifier as small as possible in order to retain the advantages of my system.

Where a plurality of coils are used in a single system as in the one illustrated in Fig. 8, the adjustment of all of the coils to the desired frequency may be made simultaneously by an'arrangement such as that illustrated in Fig. 6, in which a movement of the handle 41 produces similar movements simultane ously in both of the coils shown.

hat I claim as new and desire to secure by Letters Patent of the United States is 1. A receiving system for radio signals comprising a receiving antenna consisting of a coil having distributed capacity and inductance of such values that it is resonant for a desired frequency, and means .for simultaneously varying the values of its capacity and inductance.

2. The combination in an apparatus of the class described of a receiving antenna consisting of a coil having distributed capacity and inductance of such values that it is resonant for a desired frequency and means for adjusting the coil to vary its natural wave length.

3. A receiving system for radio signals comprising a receiving antenna consisting of a coil having distributed capacity and inductance of such values that it is resonant for a desired frequency, and means for simultaneinductance while maintaining constant the numberof turns of the coil.

- 4. An antenna consisting of a coil includw ing stationary and movable parts connected in series with one another, and means for adjusting the position of said movable parts whereby said antenna is made resonant to radio waves of different frequencies.

5. An antenna consisting of a coil including a plurality of fixed parts and a plurality of movable parts, and means for simultaneously changing the positions of said movable parts whereby simultaneous changes are produced in the capacity and inductance of said antenna.

In witness whereof, I have hereunto set my hand this 10th day of November, 1923.

ALFRED N. GOLDSMITH. 

